<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<style>
@font-face {
  font-family: dejavu;
  src: url(../fonts/DejaVuSansMono.woff);
}
.test {
  margin: 10px;
  border: 1px solid gray;
  font: 16px/24px dejavu;
  word-break: break-all;
  width: 10em;
  height: 6.5em;
  /* we use text-orientation:upright to improve the chances that our
     glyphs will have an advance of exactly 1em, as the reference
     rendering relies on this */
  text-orientation: upright;
  color: rgba(0,0,255,0.2);
}

.v-lr { writing-mode:vertical-lr; }
.v-rl { writing-mode:vertical-rl; }

.c { background: cyan; }
.b { background: blue; }
</style>
</head>

<body>

<div class="test v-lr">ABCD<span class="c">E</span><span class="b">F</span><span
 class="c">G</span><span class="b">H</span><span class="c">I</span><span
 class="b">J</span><span class="c">K</span><span class="b">L</span><span
 class="c">M</span><span class="b">N</span><span class="c">O</span><span
 class="b">P</span><span class="c">Q</span><span class="b">R</span><span
 class="c">S</span><span class="b">T</span><span class="c">U</span>VWXYZ</div>

<div class="test v-rl">ABCD<span class="c">E</span><span class="b">F</span><span
 class="c">G</span><span class="b">H</span><span class="c">I</span><span
 class="b">J</span><span class="c">K</span><span class="b">L</span><span
 class="c">M</span><span class="b">N</span><span class="c">O</span><span
 class="b">P</span><span class="c">Q</span><span class="b">R</span><span
 class="c">S</span><span class="b">T</span><span class="c">U</span>VWXYZ</div>

</body>
</html>
